The renovated George D. Aiken Center’s credentials as an environmental standout are hard to miss. The solarium in the building, which re-opened in January after an 18-month, $13 million rehab, boasts an “eco-machine” for treating waste water, nearly every interior wall is ribbed with Forest Stewardship Council-certified wood paneling, and its green roof features eight experimental watersheds.

But the most spectacular green attribute of the 40,000 sq. ft. building, home of UVM's Rubenstein School of Environment and Natural Resources, could escape notice completely: Aiken’s unusual “building envelope,” the skin between its interior and exterior walls that insulates it from the outside cold and heat.

Thanks in large part to this almost air-tight enclosure, the renovated Aiken Center is modeled to be 62 percent more energy-efficient than the original building, built in 1982, reducing its energy use from 89 kBTU’s per square foot per year, the standard measure of a building’s energy use, to 34, despite adding air conditioning, which the original building lacked.

That’s no small accomplishment. The projected energy saving qualifies Aiken as that most talked about and elusive of projects in contemporary green building -- a “deep energy retrofit,” defined as a renovated building that reduces energy by at least 30 percent over the original structure.

The reborn Aiken Center, designed by Maclay Architects of Waitsfield, Vt., is one of the first such buildings on a college campus, and one of a small number in the United States, say experts at the New Buildings Institute, which recently completed a study of 50 deep energy retrofits in the U.S. and Australia.

Wanted: paradigm shift

Aiken’s dramatic efficiency upgrade is not merely of academic interest.

America’s 120 million existing commercial buildings are one of the country’s major pollution sources, consuming 42 percent of the nation’s energy and producing more than one third of its carbon emissions, according to the Rocky Mountain Institute, the Aspen-based environmental think tank, which has made promoting deep energy retrofits one of its core missions.

It is these existing buildings, which typically undergo renovation every two or three decades, that environmentally oriented builders should be targeting, says Rubenstein School dean Mary Watzin, not new construction, as they’ve done in the past.

“Adding even a net zero new building -- one that consumes no energy at all -- is well and good, but it doesn’t really address the current energy problem,” she said. “It is older buildings like Aiken that are the issue. We need to dramatically reduce their energy consumption.”

Jaime Van Mourik, director of higher education with the Center for Green School at the U.S. Green Building Council, who calls Aiken’s energy improvement “significant and very notable,” says higher education is in need of a paradigm shift.

“Until now, the focus of the green building movement in higher ed has been on new buildings,” she said. “We need to move to renovations. There’s a tremendous amount of work to do.”

There are more than 3.48 billion square feet of existing space on college campuses, Van Mourik said. The average building in higher education uses 120 kBTU per square foot per year, according to statistics compiled by the U.S. Department of Energy.

A focus on "gas mileage"

The new Aiken Center’s enviable energy profile came about because university leaders decided to break step with convention and make energy efficiency the top design objective -- something that is rarely done in new environmental construction, let alone rehabs. Unaccountably, environmental designers have historically given short shrift to their projects' "gas mileage," as Aiken architect William Maclay puts it.

“UVM wanted to do the things that really mattered, as opposed to doing a renovation for show or even LEED points,” Maclay said. “That meant reducing the building’s energy use.”

In Aiken’s case, two key decisions related to Aiken’s building envelope -- both generalizable to other renovations -- were instrumental.

Goodbye brick

First, the university hired an envelope expert to evaluate the quality of the building’s brick exterior. The consultant found that the bricks were significantly degraded -- although they looked fine cosmetically -- and were causing a host of worsening problems, a common issue in buildings of Aiken’s vintage. They were removed and replaced, an unusual step that added cost to the project but also provided a major benefit: builders were able to insulate the exterior of the building. Exterior insulation, the standard in new construction, is a much more effective way of promoting energy efficiency than insulating a building’s interior, as is usually done in renovations.

“Initially we didn’t want to remove the brick,” said Robert Vaughan, UVM’s director of capital planning. “But once we did a true cost-benefit analysis, one that looked at the long term, the equation looked quite different.”

A unique quality control measure was the second key decision that turned a good renovation into a great one, Watzin said.

The university hired a consultant to monitor every aspect of the exterior insulating process, including the application of a spray-on air barrier, to make sure the construction crew followed the specs the architect called for -- which were unusually detailed -- to the letter.

"It seems like a small thing, but it made all the difference,” Watzin said, resulting in a building whose air barrier is so tight it’s as if it were “sealed in a plastic bag,” Maclay says.

Payback in 11 to 13 years

One reason there aren’t more deep energy retrofits, despite the great need for them, says Tristan Roberts, editor or Environmental Building News, who praised Aiken’s “huge” energy savings, is that builders often “aren’t aware of how to do things differently.”

That includes looking at financials differently, said Vaughan -- from a perspective that takes into account long term energy costs and other offsets like smaller HVAC systems.

The Aiken renovation is a case in point. The extra cost of doing a deep energy retrofit of Aiken over simply addressing deferred maintenance issues was $381,000

Based on the 40 percent energy savings the renovated building is modeled to achieve, the payback period -- assuming fuel prices will rise at a conservative rate of inflation, two percent -- is 13 years. At a five percent rise in fuel prices, the payback drops to eleven years.

"Given that the renovation is designed for at least a 50-year life, and that energy cost are all but certain to rise substantially, it was a sensible decision to make financially," said Watzin.

It was clearly the right decision to make for environmental reasons. "We've gone from a building that was an environmental embarrasment to one that, like the Rubenstein School itself, is a national leader," Watzin said. "We look forward to having a home that will inspire our faculty, students and staff to do their best work every time they walk through the doors."

Aiken was gutted and outfitted with all new mechanical systems. A comparable new building would have added $5-7 million to the renovation’s $13 million cost, university officials said.

The project was supported with a $900,000 grant from the EPA funded by an appropriation secured by Senator Patrick Leahy of Vermont.